Filler for plastic formulations based on polyurethane

ABSTRACT

The invention relates to fillers for plastics formulations based on polyurethane and the use thereof.

This application is the national phase under 35 U.S.C. § 371 of PCTInternational Application No. PCT/EP00/08569 which has an Internationalfiling date of Sep. 1, 2000, which designated the United States ofAmerica.

The invention relates to fillers for plastics formulations based onpolyurethane. The invention relates in particular to organic,crosslinked, reactive and radiation-curing plastics fillers based onpolyurethane.

Fillers for use as the filler content of plastics formulations for thepurpose of improving the physical properties thereof are sufficientlyknown. Organic fillers have been used for a long time for dentalmaterials, for example, in addition to inorganic fillers such as quartzor glasses. Bead-shaped polymers and copolymers based on methylmethacrylate are a widely used representative for this.

In addition to bead-shaped polymers, for example, precipitation polymersformed from acrylic acid and/or methacrylic acid esters for use in thedental sector are known from EP-B-0 270 915.

Advantageous features of the use of organic fillers are, inter alia, theeasy polishability of the composite materials produced therefrom, thefavourable price compared with inorganic fillers ground to an ultrafinedegree, the high transparency of the polymers obtained and the ash-freecombustibility. Because of the wide variability in the composition whichorganic fillers can have, material properties can also be influenced ina controlled manner, for example the impact strength of dental materialscan be influenced favourably by the graft copolymers mentioned inDE-A1-196 178 76.

Bead-shaped polymers and copolymers based on methyl methacrylate show ahigh tendency to swell. This is necessary in order to enable partialdissolving of the fillers by monomers, since binding of the fillers tothe resin matrix becomes possible only by the formation of aninterpenetrating network which takes place during the polymerization.However, a constant increase in the viscosity of the compositionsformulated with the fillers is caused by this tendency to swell. In thecase of prosthesis plastics, which as a rule comprise the highlysolubilizing methyl methacrylate as a main constituent of the monomermatrix, these swelling properties determine, for example, the processingtime in the pack-press technique (flask technique). The swellingproperties can be measured, for example, by measuring the processingtime as described in the international standard ISO 1567, a time frameof approx. 30 to 60 minutes being regarded as usable.

DE-C2-197 060 64 describes plastically curable one-componentcompositions based on PMMA beads and higher molecular weightcrosslinking methacrylates. Although storage stabilities of 6 months areclaimed, stiffening of the paste nevertheless already occurs within afew days at slightly elevated temperature (36° C.), this beingattributable to the increase in viscosity caused by the partialdissolving of the PMMA beads.

Although the precipitation polymers known from EP-B-0 270 915 are notpartially dissolved by the conventional (meth)acrylate monomers ofdental technology because of their high crosslinking density andtherefore also show no changes in viscosity in the course of storage,they are nevertheless not incorporated particularly well into the resinmatrix in spite of the residual double bonds present, so that theresulting composite materials have only moderate mechanical properties.The accessibility of the residual double bonds is evidently ensured toonly a limited degree.

Other organic fillers, such as plastics powders ground at roomtemperature or cryogenically, or precipitated polymer powders, showsimilar problems.

The fillers based on polyethylene, polypropylene, an ethylene-acrylicacid-acrylic acid ester terpolymer or polyurethane which arecommercially obtainable under the trade name “Coathylene” result incomposite materials with very inadequate mechanical strengths, since nobonding to the resin matrix is possible because of a lack of reactioncentres.

There is therefore a considerable demand for fillers on an organic basiswhich can be polymerized into the matrix and the swelling properties ofwhich in the conventional monomer matrices of dental technology are solow that formulations with stable viscosity properties even at elevatedtemperature and over a relatively long storage time can be realized.

The object of the present invention is to provide organic fillers whichcan satisfy the above-mentioned requirements.

This object is achieved by organic, crosslinked, reactive andradiation-curing plastics fillers based on polyurethane.

The fillers according to the invention have a high reactivity, withoutundergoing severe swelling in conventional dental monomers. They can bepolymerized into resin matrices via ethylenic double bonds, are easy andinexpensive to synthesize, and their properties can be adjusted within awide range by variation of the educts. They can be radiation-cured viathe unsaturated functionalities and are therefore particularly suitablefor use in the dental sector, but also in other industrial fields wherethe properties of the fillers according to the invention are ofadvantage.

The fillers according to the invention are obtainable by reaction of:

(A) 15 to 35 wt. %, preferably 20 to 30 wt. % of one or moreradiation-curing (meth)acrylate-based compounds with OH numbers of 40 to700 mg KOH/g,

(B) 15 to 40 wt. %, preferably 20 to 35 wt. % of one or more polyolswith a molecular weight of 500 to 6,000 g/mol,

(C) 0 to 15 wt. %, preferably 0 to 10 wt. % of one or more polyols witha molecular weight of less than 500 g/mol,

(D) 1 to 10 wt. %, preferably 1 to 7 wt. % of at least one compoundwhich is mono- and/or difunctional in the sense of the isocyanatereaction, which additionally contains anionic groups or functionalgroups which can be converted into anionic groups,

(E) 24 to 69 wt. %, preferably 34 to 55 wt. % of one or morepolyisocyanates,

and subsequent chain lengthening or crosslinking of the resultingproduct from (A) to (E) with

(F) 0.5 to 10 wt. %, preferably 0.5 to 5 wt. %, relative to the totalweight of components (A) to (E), of a mixture of one or more diamineswith a polyamine of functionality greater than 2,

at least 30 wt. %, preferably at least 50 wt. % of component (F)comprising polyamine of functionality greater than 2.

Radiation-curing but aqueous dispersions of a similar composition areknown from the coatings industry. DE-A-195 25 489 and DE-A44 34 554describe, for example, polyester-(meth)acrylate-urethane dispersionsbased on polyester-meth)acrylate prepolymers containing hydroxyl groups.These are obtainable by polyaddition of polyester-(meth)acrylateprepolymers containing hydroxyl groups and compounds which are reactivetowards isocyanate groups with polyisocyanates and subsequent reactionwith polyfunctional amines. These aqueous dispersions form films ondrying, and thus no solid particles which can be used as a filler.

Surprisingly, however, it has been found that by reaction of theabove-mentioned components (A) to (E) with subsequent crosslinking bycomponent (F), the fillers according to the invention are obtained afterstripping off the solvent. It is particularly advantageous here thatafter the crosslinking with (F) the fillers can be obtained withoutadditional working-up steps.

Component (A) comprises radiation-curing (meth)acrylate-based compoundswhich have OH numbers from 40 to 700 mg KOH/g according to DIN 53 240.The term (meth)acrylate is used in this specification to representmethacrylate and/or acrylate.

Suitable components (A) are, for example, polyester-(meth)acrylateprepolymers containing hydroxyl groups such as are described in U.S.Pat. No. 4,206,205, DE-OS40 40 290, DE-OS-33 16 592, DE-OS-37 04 098 andin “UV & EB Curing Formulations for Printing Inks Coatings and Paints”,ed. R. Holman and P. Oldring, published by SITA Technology, London(England) 1988, p. 36 et seq. Alternatively, polyepoxy(meth)acrylateprepolymers containing hydroxyl groups which are accessible by reactionof polyepoxides with (meth)acrylic acid, and/orpolyurethane-(meth)acrylate prepolymers containing hydroxyl groups canalso be used. The use of polyepoxy(meth)acrylate prepolymers containinghydroxyl groups, such as2,2-bis-4-(3-methacryloxy-2-hydroxypropyl)phenylpropane (bis-GMA),2,2-bis-4-(3-acryloxy-2-hydroxypropyl)phenylpropane (bis-GA), and of(meth)acrylate esters containing hydroxyl groups, such as glycerolmono(meth)acrylate, trimethylolpropane mono(meth)acrylate orpentaerythritol di(meth)acrylate, is particularly preferred.

Polyols of component (B) have a molecular weight of 500 to 6,000 g/moland can be in a linear or slightly branched form. The polyols can betaken from the known chemical classes of polymeric polyols which areused in polyurethane syntheses or formulations. Examples which may bementioned are polyester-, polyester-amide-, polyether-, polythioether-,polycarbonate-, polyacetal-, polyolefin-, polysiloxane- andpoly(meth)acrylate-polyols.

The polyester-polyols are reaction products of low molecular weightpolyols with low molecular weight polycarboxylic acids.

Suitable low molecular weight polyols or polyol mixtures are, forexample, ethylene glycol, propylene glycol, 1,4-butanediol,1,6-hexanediol, diethylene glycol, triethylene glycol, neopentylglycol,1,4-bis(hydroxymethyl)-cyclohexane, dipropylene glycol. Glycerol,trimethylolpropane or pentaerythritol, for example, are suitable aspolyols of higher functionality, a proportion of which can be co-used tointroduce branchings into the polyester molecule. 1,6-hexanediol,neopentylglycol and trimethylolpropane are particularly preferred.

The low molecular weight polycarboxylic acids can be aliphatic,cycloaliphatic, aromatic and/or heterocyclic in nature. Instead of thefree polycarboxylic acids, it is also possible to use correspondingpolycarboxylic acid anhydrides or polycarboxylic acid esters with loweralcohols. Examples which may be mentioned are: succinic acid, adipicacid, sebacic acid, azelaic acid, phthalic acid, isophthalic acid,phthalic anhydride, tetrahydrophthalic anhydride, glutaric anhydride,maleic acid, maleic anhydride, fumaric acid and dimethyl terephthalate.Adipic acid is particularly preferred.

Suitable polyester polyols are obtainable from Bayer under the name“Desmophen”.

Polyesters which are accessible by polymerization of lactones, such ascaprolactone, in combination with a polyol can also be used.Polyester-amide-polyols can be obtained by using a proportion ofamino-alcohols, such as ethanolamine, in the polyester formationmixture.

Polyether-polyols which can be used comprise products which areaccessible by polymerization of a cyclic oxide, for example ethyleneoxide, propylene oxide or tetrahydrofuran, or by addition of one or moreof these oxides to polyfunctional initiators, such as water, ethyleneglycol, propylene glycol, diethylene glycol, cyclohexanedimethanol,glycerol, trimethylolpropane, pentaerythritol or bisphenol A.Particularly suitable polyether polyols are polyoxypropylenediols and-triols, poly(oxyethylene-oxypropylene)diols and -triols, which areobtained by simultaneous or successive addition of ethylene andpropylene oxide to suitable initiators, and polytetramethylene etherglycols, which are formed by polymerization of tetrahydrofuran.

Polythioether-polyols which can be used are, inter alia, products whichare obtained by condensation of thiodiglycol by itself or with otherglycols, dicarboxylic acids, formaldehyde, amino-alcohols oraminocarboxylic acids.

Polycarbonate-polyols which can be used are, inter alia, products whichresult by reaction of diols, such as 1,3-propanediol, 1,4-butanediol,1,6-hexanediol, diethylene glycol or tetraethylene glycol, with diarylcarbonates, such as diphenyl carbonate, or with phosgene.

Suitable polyacetal-polyols are compounds which can be prepared byreaction of glycols, such as diethylene glycol, triethylene glycol or1,6-hexanediol, with formaldehyde or by polymerization of cyclicacetals.

Suitable polyolefin-polyols are, inter alia, butadiene homo- andcopolymers with terminal hydroxyl groups.

Suitable polysiloxane-polyols are marketed, for example, by Goldschmidtunder the name “Tegomer HSi”.

Suitable poly(meth)acrylate-polyols are obtainable, for example, fromTego under the name “Tegodiol”.

Polyester-polyols and polycarbonate-polyols with a molecular weight of500 to 6,000 g/mol, and in particular with a molecular weight of 500 to3,000 g/mol, are particularly preferred as component (B). Such compoundsare commercially obtainable, for example, from Daicel under the name“Placcel”.

Suitable polyols of component (C) with a molecular weight of less than500 g/mol are the following: aliphatic, cycloaliphatic, aromatic and/orheterocyclic compounds such as have already been mentioned substantiallyfor component (B) in the context of the description for building up thepolyester-polyols. Particularly preferred polyols of component (C) areneopentylglycol and trimethylolpropane.

Component (D) is, for example, at least one hydroxycarboxylic acidand/or aminocarboxylic acid and/or aminosulphonic acid and/orhydroxysulphonic acid. These compounds are incorporated into theprepolymer, which results from components (A) to (E) in the end, via theamino and/or hydroxy groups which are reactive towards the isocyanatesof component (E). The compounds of component (D) acquire dispersingproperties by neutralization of the carboxyl groups and/or sulphonicacid groups with organic and/or inorganic bases.

Examples which may be mentioned as representative of component (D) are:malic acid, glycolic acid, glycine, taurine, aminocaproic acid and2-amino-ethylaminosulphonic acid. The preferred representatives ofcomponent (D) include 2,2-bis hydroxymethyl)alkanemonocarboxylic acidswith a total of 5 to 8 carbon atoms according to the general formula(1):

in which R represents a linear, branched or cyclic alkyl radical with 1to 7 C atoms. 2,2-dimethylolpropionic acid is a vary particularlypreferred builder component (D).

Polyisocyanates which are suitable as component (E) are aliphatic,cycloaliphatic and/or aromatic in nature.

Examples of suitable polyisocyanates are: 1,6-hexamethylene diisocyanate(HDI), tetramethylene diisocyanate, isophorone diisocyanate,4,4′-dicyclohexylmethane diisocyanate, 1,4-phenylene diisocyanate, 2,6-and 2,4-toluene diisocyanate, 1,5-naphthylene diisocyanate, 2,4′- and4,4′-diphenylmethane diisocyanate. It is of course also possible to useor to co-use a proportion of the polyisocyanates of higher functionalitywhich are known per se in polyurethane chemistry, or also of modifiedpolyisocyanates, for example containing carbodiimide groups, allophanategroups, isocyanurate groups, urethane groups and/or biuret groups whichare known per se. Particularly preferred isocyanates are cycloaliphaticisocyanates, such as isophorone diisocyanate and4,4′-dicyclohexylmethane diisocyanate.

Components (A) to (E) are initially introduced into a reactor or meteredin individually and reacted under anhydrous conditions in a temperaturerange from 30° C. to 130° C. to give an NCO-containing prepolymer. Theequivalent ratio of isocyanate groups to compounds which are reactivetowards isocyanate groups is 1.1:1 to 3:1, preferably 1.5:1 to 2:1.Carboxyl groups which are introduced into the prepolymer, for example,by co-using 2,2-dimethylolpropionic acid are not taken into account inthe calculation of the equivalent ratio. The isocyanate polyadditionreaction can be carried out in the presence of catalysts which are knownin polyurethane chemistry, such as organotin compounds. It isfurthermore possible to use an organic solvent before, during or afterthe prepolymer preparation in order to control the viscosity.

Suitable solvents are, for example, acetone, 2-butanone,tetrahydrofuran, dioxane, dimethylformamide, N-methyl-2-pyrrolidone(NMP), ethyl acetate, alkyl ethers of ethylene glycol and propyleneglycol and aromatic hydrocarbons. The use of water-miscible, low-boilingsolvents, such as acetone, which can be removed by distillation from thepolyurethane-polyurea dispersions prepared, is particularly preferred.

Before dispersion of the prepolymer prepared from components (A) to (E)in water and chain lengthening or crosslinking with component (F), thepotential ionic groups present in the prepolymer are converted intoionic groups, for example by neutralization. Tertiary amines arepreferably used for the neutralization, in particular if buildercomponents (D) which contain carboxyl groups are used. Such tertiaryamines are, for example, triethylamine, tri-n-butylamine,N-methymorpholine, N,N-dimethylethanolamine, N-methylpiperidine,N-methylpiperazine and triethanolamine. The use of inorganic bases, suchas sodium hydroxide or potassium hydroxide, as the neutralizing agent isalso possible, although less preferred. It is also possible forcomponent (D) already to be used in the neutralized form in thepreparation of the prepolymer.

The formation of stable aqueous dispersions is ensured by neutralizationof the potential ionic groups. In general, at least 80%, but preferably100% of the potential ionic groups are converted into ionic groups byneutralization. The neutralization reaction is as a rule carried outhere at temperatures below 100° C., and preferably in the temperaturerange from 30 to 80° C.

The conversion of the neutralized NCO-containing prepolymers intoaqueous dispersions is carried out by the methods known in polyurethanechemistry. One possibility is the addition of the dispersing water,which contains component (F), to the prepolymer. In this process, theorganic prepolymer initially forms the continuous phase. On furtheraddition of water a phase inversion takes place and the water becomesthe continuous phase.

In another dispersing possibility, the neutralized prepolymer is addedto the dispersing water. Component (F) can be initially introduced herein the dispersing water, or alternatively can be added only afterdispersing of the prepolymer.

The dispersing step is preferably carried out in a temperature rangefrom 20 to 40° C. The dispersibility of the prepolymers in water can beimproved here by the additional use of external emulsifiers. Suitableexternal emulsifiers are, for example, alkyl sulphates, for example witha chain length of 8 to 18 C atoms, and aryl and alkyl ether-sulphateswith 8 to 18 C atoms in the hydrophobic radical and 1 to 40 ethyleneoxide (EO) or propylene oxide (PO) units.

It is furthermore possible to use:

sulphonates, for example alkylsulphonates with 8 to 18 C atoms,alkylarylsulphonates with 8 to 18 C atoms, esters and half-esters ofsulphosuccinic acid with monohydric alcohols or alkylphenols with 4 to15 C atoms, it also being possible for the alcohols or alkylphenols tobe ethoxylated with 1 to 40 EO units,

alkali metal and ammonium salts of carboxylic acids, in particular with8 to 20 C atoms in the alkyl, aryl, alkaryl or aralkyl radical,

phosphoric acid partial esters and alkali metal and ammonium saltsthereof, for example alkyl and alkaryl phosphates with 8 to 20 C atomsin the organic radical,

alkyl ether- or alkaryl ether-phosphates with 8 to 20 C atoms in thealkyl or alkaryl radical and 1 to 40 EO units,

alkyl polyglycol ethers with 2 to 40 EO units and alkyl radicals from 4to 20 C atoms,

alkylaryl polyglycol ethers with 2 to 40 EO units and 8 to 20 C atoms inthe alkyl and aryl radicals,

ethylene oxide/propylene oxide (EO/PO) block copolymers with 8 to 40 EOor PO units,

fatty acid polyglycol esters with 6 to 24 C atoms and 2 to 40 EO unitsand

alkyl polyglycosides.

The alkyl radicals can be, for example, in each case branched,unbranched or cyclic in nature or can have a mixture of these features.

Component (F) describes mixtures of one or more diamines with one ormore polyamines of functionality greater than 2. The diamines lead to achain lengthening and therefore to a build up in the molecular weight ofthe prepolymer, while the polyamine with a functionality greater than 2effects a crosslinking of the molecular structure. The reaction of theprepolymer with the constituents of component (F) takes place in anaqueous medium. The compounds of component (F) therefore preferably havea higher reactivity towards isocyanate groups compared with water. Theamount of component (F) to be used depends on the unreacted isocyanategroups of the prepolymer still present. The isocyanate content of theprepolymer is determined in accordance with DIN 53 185.

Suitable diamines which may be mentioned by way of example are:1,2-diaminoethane, 1,6-diaminohexane, piperazine,2,5-dimethylpiperazine, 1-amino-3-aminoethyl-3,5,5-trimethylcyclohexane,4,4′-diaminodicyclohexylmethane, 1,4-diaminocyclohexane and/or1,2-propylenediamine. Hydrazine, amino acid hydrazides, bishydrazidesand bis-semicarbazides are also suitable as chain lengtheners.1,2-diaminoethane is a particularly preferred diamine.

Examples of polyamines with a functionality greater than 2 arediethylenetriamine, triethylenetetramine, tetraethylenepentamine,pentaethylenehexamine, polyethyleneimines and melamine. The use ofdiethylenetriamine is particularly preferred.

The filler according to the invention is present in the solution indispersed form for example in a concentration of 20 to 60 wt. %, inparticular between 25 and 45 wt. %. The pure filler can be obtained bystripping off the solvent, for example by means of a vacuum or also byspray drying. Another possibility for isolating the filler from theaqueous dispersion is by coagulation of the dispersion by means of theaddition of salt or by addition of polar solvents. Spray drying isparticularly preferred, since the fillers according to the invention areobtained in a small particle size in this process and can be useddirectly in further formulations.

The fillers according to the invention are particularly suitable for thepreparation of dental compositions. Such formulations preferablycomprise the following components:

(C1) 1 to 40 wt. %, in particular 5 to 30 wt. % of filler according tothe invention,

(C2) 10 to 98.9 wt. %, in particular 14 to 94.9 wt. % of one or moreethylenically unsaturated polymerizable monomers based on di- orpolyfunctional (meth)acrylates,

(C3) 0 to 75 wt. %, in particular 0 to 50 wt. % of conventional fillers,

(C4) 0.1 to 3 wt. %, in particular 0.1 to 2 wt. % of initiators and,where appropriate, activators,

(C5) 0 to 10 wt. %, in particular 0 to 5 wt. % of additives, whereappropriate pigments, thixotropy auxiliaries, plasticizers.

The compositions formulated from the fillers according to the inventionare distinguished by particularly good mechanical properties andconsiderablc handling advantages. Because of the good viscoelasticitythey are thus particularly hard, but at the same time flexible. Thereactive (meth)acrylate groups enable bonding of the fillers into thematrix of the formulation. Due to the high molecular weights the fillershave a maximum biocompatibility and have no toxicologically unacceptableproperties at all. With suitable choice of the educts, the formulationsburn virtually ash-free.

At least bifunctional acrylic acid and/or methacrylic acid esters areused as component (C2). These can be monomeric and polymeric acrylatesand methacrylates. For example, the long-chain monomers of U.S. Pat. No.3,066,112 based on bisphenol A and glycidyl methacrylate or derivativesthereof formed by addition of isocyanates can advantageously be used.Compounds of the type bisphenol A diethyloxy(meth)acrylate and bisphenolA dipropyloxy(meth)acrylate are also suitable. The oligo-ethoxylated andoligo-propoxylated bisphenol A diacrylic and dimethacrylic acid esterscan furthermore be used.

The acrylic acid and methacrylic acid esters of at least bifunctionalaliphatic alcohols are also particularly suitable, for exampletriethylene glycol di(meth)acrylate, ethylene glycol di(meth)acrylate,hexanediol di(meth)acrylate and trimethylolpropane tri(meth)acrylate.

The diacrylic and dimethacrylic acid esters ofbis(hydroxymethyl)-tricyclo[5.2.1.0^(2,6)]-decane, which are mentionedin DEC-28 16 823, and the diacrylic and dimethacrylic acid esters ofbis(hydroxymethyl)-tricyclo[5.2.1.0^(2,6)]-decane compounds lengthenedwith 1 to 3 ethylene oxide and/or propylene oxide units are alsoparticularly suitable.

The methacrylic acid esters described in EP-A-0 235 826, for exampletriglycolic acidbis[3(4)-methacryloxymethyl-8(9)-tricyclo[5.2.1.0^(2.6)]-decylmethylester], are also particularly suitable monomers.

Mixtures of monomers and/or of unsaturated polymers prepared therefromcan of course also be used.

Conventional fillers according to component (C3) can be inorganicfillers, for example quartz, ground glasses, fluorides which are notwater-soluble, such as CaF₂, silica gels and silica, in particularpyrogenic silica or granules thereof. For better incorporation into thematrix it may be advantageous to hydrophobize these fillers and, ifappropriate, additives which are opaque to x-rays. In a preferredembodiment, all the inorganic fillers used are silanized, preferablywith trimethoxymethacryloxypropylsilane. The amount of silane used isusually 0.5 to 10 wt. %, relative to the inorganic fillers, preferably 1to 6 wt. %, very particularly preferably 2 to 5 wt. %, relative to theinorganic fillers. Conventional hydrophobizing agents are silanes, forexample trimethoxymethacryloxypropylsilane. The maximum average particlesize of the inorganic fillers is preferably 15 μm, in particular 8 μm.Fillers with an average particle size of <3 μm are very particularlypreferably used.

Fillers which release fluoride, for example complex inorganic fluoridesfrom DE-A-44 45 266, can also be used.

Conventional bead-shaped polymers and copolymers based on methylmethacrylate, which are obtainable, for example, from Röhm under thename “Piexidon” or “Plex” can furthermore also be used.

By initiators of component (C4) are meant initiator systems which effectradical polymerization of the at least bifunctional monomers, forexample photoinitiators or so-called redox initiator systems, but alsothermal initiators.

Suitable photoinitiators are, for example, α-diketones, such ascamphorquinone, in combination with secondary and tertiary amines, ormono- and bisacylphosphine oxides, such as2,4,6-trimethylbenzoyidiphenyl-phosphine oxide andbis-(2,6-dichlorobenzoyl)-4-n-propylphenyl-phosphine oxide. However,other compounds of this type such as are described in the EuropeanPatent specification publications EP-A-0 073 413, EP-A-0 007 508, EP-A-0047 902, EP-A-0 057 474 and EP-A-0 184 095 are also suitable.

Suitable redox initiator systems are organic peroxide compounds togetherwith so-called activators. Possible organic peroxide compounds here are,in particular, compounds such as lauroyl peroxide, benzoyl peroxide andp-chlorobenzoyl peroxide and p-methylbenzoyl peroxide.

Suitable activators are, for example, tertiary aromatic amines, such asthe N,N-bis-(hydroxyalkyl)-3,5-xylidines known from U.S. Pat. No.3,541,068 and the N,N-bis-(hydroxyalkyl)-3,5-di-t-butylanilines knownfrom DE-A-26 58 530, in particularN,N-bis-(β-oxybutyl)-3,5-di-t-butylaniline andN,N-bis-(hydroxyalkyl)-3,4,5-trimethylanilines.

The barbituric acids and barbituric acid derivatives described inDE-B-14 95 520 and the malonylsulphamides described in EP-A-0 059 451are also particularly suitable activators. Preferred malonylsulphamidesare 2,6-dimethyl-4-isobutylmalonylsulphamide,2,6-diisobutyl-4-propylmalonylsulphamide,2,6-dibutyl-4-propylmalonylsulphamide,2,6-dimethyl-4-ethylmalonylsulphamide and2,6-dioctyl-4-isobutylmalonylsulphamide.

For further acceleration, the polymerization is preferably carried outhere in the presence of heavy metal compounds and ionic halogen orpseudohalogen. Copper is particularly suitable as the heavy metal andthe chloride ion as the halide. The heavy metal is suitably used in theform of soluble organic compounds. The halide and pseudohalide ions arealso suitably used in the form of soluble salts, and the soluble aminehydrochlorides and quaternary ammonium chloride compounds may bementioned as examples.

If the dental compositions according to the invention contain a redoxinitiator system of organic peroxide and activator as component (C4),the peroxide and activator are preferably present in parts of the dentalcomposition according to the invention which are spatially separatedfrom one another and are mixed homogeneously with one another onlyimmediately before the use of the dental composition according to theinvention. If the dental composition according to the invention containsas (C4) organic peroxide, copper compound, halide and malonylsulphamideand/or barbituric acid side by side, it is particularly useful for theorganic peroxide, malonylsulphamide and/or barbituric acid and thecombination of copper compound/halide to be present in threeconstituents which are spatially separated from one another. Forexample, the combination of copper compound/halide, polymerizablemonomers and fillers can be kneaded to a paste and the other componentscan be kneaded to two separate pastes in the manner described above ineach case with a small amount of fillers or, in particular, thixotropyauxiliaries, such as silanized silica, and a plasticizer, for examplephthalate. On the other hand, the polymerizable monomers can also bepresent together with organic peroxide and fillers.

Soluble organic polymers can be used as component (C5), for example, toincrease the flexibility of the compositions. Suitable polymers are, forexample, polyvinyl acetate and copolymers based on vinyl chloride/vinylacetate, vinyl chloride/vinyl isobutyl ether and vinyl acetate/maleicacid dibutyl ether. Dibutyl, dioctyl and dinonyl phthalates or adipatesand higher molecular weight polyphthalic acid esters and adipic acidesters are particularly suitable as additional plasticizers. In additionto pyrogenic silicas, modified laminar silicates (bentonites) or organicmodifying agents, for example based on hydrogenated castor oilderivatives, can also be used as thixotropy auxiliaries.

Dental materials which comprise the fillers according to the inventioncan be, for example, filling materials, cements, temporary crown andbridge materials, veneer plastics, prosthesis materials, orthodonticmaterials, plastics for sealing fissures, modelling plastics or modelplastics.

The fillers according to the invention are also suitable for use informulations for gluing, coating and embedding substrates, for exampleas a filler for stopper compositions or for improvements to theproperties of plastics in general.

The invention is described in more detail in the following by examples,without limiting it.

Polyurethane Filler PREPARATION EXAMPLE 1

A 2 1 3-necked flask fitted with a thermometer, reflux condenser andmechanical stirrer was charged with 200 g bis-GMA (component A), 40.2 gdimethylolpropionic acid (component D), 23.1 g 1,6-hexanediol (componentC), 195.8 g of a polyester-polyol (component B) prepared fromterephthalic acid/neopentylglycol with a molecular weight of 1,000g/mol, 420 g acetone, 333 g isophorone diisocyanate (component E) and0.1 g dibutyltin dilaurate. The reaction mixture was heated for 5 hoursat 60° C., until the isocyanate content had fallen to 3.9%. The reactorwas cooled to 20° C. and the mixture was neutralized with 27.2 gtriethylamine.

The prepolymer solution obtained is dispersed in 1,152 g deionized waterat 23° C., while stirring, and subsequently crosslinked by addition of7.0 g ethylenediamine (component F) and 8.0 g diethylenetriamine(component F). After twenty hours the dispersion had a pH value of 7.7and a solids content of 34.5%.

The dispersion was dried in a thin layer in a drying cabinet at 40° C.The granules obtained were brought to a particle size distribution of50% <60 μm, 99% <200 μm by grinding.

PREPARATION EXAMPLE 2

A 2 1 3-necked flask fitted with a thermometer, reflux condenser andmechanical stirrer was charged with 200 g bis-GMA (component A), 40.2 gdimethylolpropionic acid (component D), 214.5 g ethoxylated bisphenol A(component B) with a molecular weight of 550, 356 g tetrahydrofuran, 333g isophorone diisocyanate (component E) and 0.1 g dibutyltin dilaurate.The reaction mixture was heated for 5 hours at 60° C., until theisocyanate content had fallen to 3.5%. The reactor was cooled to 20° C.and the mixture was neutralized with 27.2 g triethylamine.

The prepolymer solution obtained is dispersed in 1,296 g deionized waterat 23° C., while stirring, and subsequently crosslinked by addition of 9g ethylenediamine (component F) and 7.8 g diethylenetriamine (componentF). After twenty hours the dispersion had a pH value of 7.9 and a solidscontent of 33.5%.

The dispersion was dried in a thin layer in a drying cabinet at 40° C.The granules obtained were brought to a particle size distribution of50% <60 μm, 99% <200 μm by grinding.

Dental Model Materials PREPARATION EXAMPLE 3

1. Preparation of a Monomer Solution

The constituents listed in the following table are stirred in a conicalflask in a suitable red light room until a homogeneous solution isobtained.

74.27 g Bis-GMA stab. with 200 ppm hydroquinone monomethyl ether (HQME)18.57 g Bis(hydroxymethyl)-tricyclo[5.2.1.0^(2,6)]-decane diacrylatestab. with 100 ppm HQME and 180 ppm Jonol  0.40 gBis-(2,6-dichlorobenzoyl)-4-n-propylphenyl-phosphine oxide  6.76 gPoly(phthalic acid 1,6-hexanediol ester) with a viscosity of 1,200 to1,300 mPas

2. Preparation of the Pastes

The pastes described in the following are prepared therefrom using alaboratory kneader. The filler additions are carried out successively,and after each part addition kneading is carried out under reducedpressure (200 mbar) until the paste is homogeneous. The kneading timesare between 6 h and 9 h. The amounts data are in percent by weight.

Com-1 Com-2 Com-3 Com-4 Com-5 Monomer solution 83% 69% 69% 67% 72%Precipitation polymer^(#)  17%* 13% 13% 13% 13% PU filler 1 18% PUfiller 2 18% Plex-6690-F 15% Coathylene TB 2957 20% *a higher degree offilling cannot be achieved ^(#)according to preparation example 3 ofEP-0 270 915

The pastes obtained are kept for 1 day at 50° C. A certain increase inviscosity again took place here in all the pastes.

The pastes prepared in this way show, after curing (photopolymerizationapparatus Visio beta vario, ESPE) the mechanical properties listed inthe following:

Com-1 Com-2 Com-3 Com-4 Com-5 Flexural strength [MPa] 48 77 69 35 27 Emodulus [MPa] 1,300 2,200 1,980 990 1,020 Ball indentation hardness 79100 106 43 41 [MPa]

If the pastes obtained are stored a different temperatures, thefollowing observations can be achieved:

Storage Tempera- time ture Com-1 Com-2 Com-3 Com-4 Com-5 1 week  4° C.OK OK OK OK OK 23° C. OK OK OK OK OK 36° C. OK OK OK OK stiffened 1month  4° C. OK OK OK OK OK 23° C. OK OK OK OK stiffened 36° C. OK OK OKOK — 6 months  4° C. OK OK OK OK stiffened 23° C. OK OK OK OK — 36° C.OK OK OK tacky, — rubbery 12 months  4° C. OK OK OK OK — 23° C. OK OK OKtacky, — rubbery 36° C. OK OK OK — —

Temporary Crown and Bridge Materials PREPARATION EXAMPLE 4

1. Preparation of a Catalyst Paste

The constituents listed in the table are mixed in a kneader until ahomogeneous paste with a viscosity of 78 Pas is obtained. The kneadingtimes are between 4 h and 7.5 h.

38.9 g acetylated bisphenol A with a degree of ethoxylation of 4 5 gpoly(phthalic acid 1,6-hexanediol ester) with a viscosity of 1,200 to1,300 mPas 51 g SrAIB silicate glass (d₅₀ = 10 μm, silanized with 1% 3-methacroylpropoxytrimethoxysilane) 4.1 g di(4-methylbenzoyl) peroxide 1g pyrogenic silica

2. Preparation of the Base Pastes

The constituents listed in the table are mixed in a kneader until ahomogeneous paste with a viscosity of between 8-12 Pas is obtained. Thekneading times are between 2.5 h and 4.5 h. The amounts data are inpercent by weight.

TCB-1 TCB-2 2,2-Bis-(4-di(ethoxy)phenyl)-propane 46.5%   46.5%  dimethacrylate 7,7,9-Trimethyl-4,13-dioxo-3,14-dioxa-5,12- 31% 31%diazahexadecane 1,16-dioxydimethacrylate SrAIB silicate glass (d₅₀ = 10μm, silanized with 18% 13% 1% 3-methacroylpropoxytrimethoxysilane) PUfiller according to example 2  0%  5% Pyrogenic silica  3%  3%N,N-Bis-(2-hydroxyethyl)-4-methylaniline 1.5%  1.5% 

The pastes prepared in this way are mixed in a ratio of 4:1(base:catalyst). The cured formulations have the mechanical propertieslisted in the following:

TCB-1 TCB-2 Flexural strength [MPa] 73 71 E modulus [MPa] 1,300 1,420Impact strength [mJ/mm²] 3.23 5.18

What is claimed is:
 1. Filler for plastics formulations based onpolyurethane, obtained by reaction of the following components (A) to(E): (A) 15 to 35 wt. % of one or more radiation-curing(meth)acrylate-based compounds with OH numbers of 40 to 700 mg KOH/g (B)15 to 40 wt. % of one or more polyols with a molecular weight of 500 to6,000 g/mol (C) 0 to 15 wt. % of one or more polyols with a molecularweight of less than 500 g/mol (D) 1 to 10 wt. % of at least one compoundwhich is mono- and/or difunctional in the sense of the isocyanatereaction, which additionally contains anionic groups or functionalgroups which can be converted into anionic groups (E) 24 to 69 wt. % ofone or more polyisocyanates, and subsequent crosslinking the resultingproduct from (A) to (E) with component (F) (F) 0.5 to 10 wt. % relativeto the total weight of components (A) to (E), of a mixture of at leastone diamine with a polyamine of functionality greater than 2, at least30 wt. % of component (F) comprising polyamine of functionality greaterthan
 2. 2. Filler according to claim 1, wherein components (A) to (F)are defined as follows: (A) one or more of the following compounds:polyester-(meth)acrylate prepolymer containing hydroxyl groups,polyepoxy(meth)acrylate prepolymer containing hydroxyl groups,polyurethane-(meth)acrylate prepolymer containing hydroxyl groups and(meth)acrylate ester containing hydroxyl groups, (B) one or more of thefollowing compounds: polyester-, polyester-amide-, polyether-,polythioether-, polycarbonate-, polyacetal-, polyolefin-, polysiloxane-and poly(meth)acrylate-polyols, (C) one or more of the followingcompounds: ethylene glycol, propylene glycol, 1,4-butanediol,1,6-hexanediol, diethylene glycol, triethylene glycol, neopentylglycol,1,4-bis (hydroxymethyl)-cyclohexane, dipropylene glycol, glycerol,trimethylolpropane or pentaerythritol, (D) one or more of the followingcompounds: malic acid, glycolic acid, glycine, taurine, aminocaproicacid, 2-amino-ethylaminosulphonic acid,2,2-bis(hydroxymethyl)-alkanemonocarboxylic acids with a total of 5 to 8carbon atoms according to the general formula (1):

 in which R represents a linear, branched or cyclic alkyl radical with 1to 7 C atoms, (E) one or more of the following compounds:1,6-hexamethylene diisocyanate, tetramethylene diisocyanate, isophoronediisocyanate, 4,4′,-dicyclohexylmethane diisocyanate, 1,4-phenylenediisocyanate, 2,6- and 2,4-toluene diisocyanate, 1,5-naphthylenediisocyanate, 2,4′- and 4,4′-diphenylmethane diisocyanate,polyisocyanates of higher functionality or modified isocyanates, such aspolyisocyanates containing carbodiimide groups, allophanate groups,isocyanurate groups and/or biuret groups, (F) one or more of thefollowing compounds: 1,2-diaminoethane, 1,6-diaminohexane, piperazine,2,5-dimethylpiperazine, 1-amino-3-aminoethyl-3,5,5-trimethylcyclohexane,4,4′-diaminodicyclohexylmethane, 1,4-diaminocyclohexane,1,2-propylenediamine, hydrazine, amino acid hydrazides, bishydrazides,bis-semicarbazides and polyamines with a functionality greater than 2.3. Filler according to claim 1 or 2, wherein components (A) to (F) aredefined as follows: (A) one or more of the following compounds:2,2-bis-4-(3-methacryloxy-2-hydroxypropyl)phenylpropane,2,2-bis-4-(3-acryloxy-2-hydroxypropyl) phenylpropane, glycerolmonoacrylate, glycerol monomethacrylate, trimethylolpropanemonoacrylate, trimethylolpropane monomethacrylate, pentaerythritoldiacrylate, pentaerythritol dimethacrylate, (B) one or more of thefollowing compounds: polyester- and polycarbonate-diols, (C) one or moreof the following compounds: neopentylglycol, trimethylolpropane,1,6-hexanediol, (D) 2,2-dimethylolpropionic acid, (E) isophoronediisocyanate and/or 4,4′,dicyclohexylmethane diisocyanate, (F) asdiamine: 1,2-diamionethane; as polyamine with a functionality greaterthan 2: diethylenetriamine.
 4. A dental filling composition comprisingthe filler as disclosed in claim 1 or
 2. 5. A material for the dentalfilling, dental cementing, temporary crown and bridge materials, veneerplastics, prosthesis materials, orthodontic materials, plastics forsealing fissures, modeling plastics or model plastics wherein saidmaterial is comprised of the filler as disclosed in claim 1 or
 2. 6. Aformulation for coating, gluing or embedding substrates comprising thefiller as disclosed in claim 1 or
 2. 7. Process for the preparation offillers for plastics formulations based on polyurethane, comprising thefollowing steps of: (1) reaction of a mixture of: (A) 15 to 35 wt. % ofone or more radiation-curing (meth)acrylate-based compounds with OHnumbers of 40 to 700 mg KOH/g (B) 15 to 40 wt. % of one or more polyolswith a molecular weight of 500 to 6,000 g/mol (C) 0 to 15 wt. % of oneor more polyols with a molecular weight of less than 500 g/mol (D) 1 to10 wt. % of at least one compound which is mono- and/or difunctional inthe sense of the isocyanate reaction, which additionally containsanionic groups or functional groups which can be converted into anionicgroups (E) 24 to 69 wt. % of one or more polyisocyanates, (2)neutralization of the potential ionic groups present in the prepolymers;(3) dispersing in water and crosslinking with: (F) 0.5 to 10 wt. %,relative to the total composition of components (A) to (E), of a mixtureof at least one diamine with a polyamine of functionality greater than2; at least 30 wt. % of component (F) comprising polyamine offunctionality greater than 2; (4) working up.
 8. A compositioncomprising the filler according to claim 1 or 2 present in an amount offrom 1 to 40 wt. % and further comprising: (C1) 10 to 98.8 wt. % of oneor more ethylenically unsaturated polymerizable monomers based on di- orpolyfunctional (meth)acrylates, (C2) 0 to 75 wt. % of conventionalfillers, (C3) 0.1 to 3 wt. % of initiators, (C4) 0 to 10 wt. % ofadditives, and optionally containing one or more members selected fromthe group consisting of activators pigments, thixotrophy auxiliaries,and plasticizers.
 9. The filler according to claim 1, wherein at least50 wt. % of component (F) is a polyamine having a functionality greaterthan
 2. 10. A method of manufacturing a member selected from the groupconsisting of filling materials, cements, temporary crown and bridgematerials, veneer plastics, prosthesis materials, orthodontic materials,plastics for sealing fissures, modeling plastics and model plasticswherein said method comprises the steps of reacting the components (A)to (E) and subsequently crosslinking the resulting product from (A) to(E) with component (F) according to claim
 3. 11. A compositioncomprising the filler according to claim 3 present in an amount of from1 to 40 wt. % and further comprising: (C1) 10 to 98.8 wt. % of one ormore ethylenically unsaturated polymerizable monomers based on di- orpolyfunctional (meth)acrylates, (C2) 0 to 75 wt. % of conventionalfillers, (C3) 0.1 to 3 wt. % of initiators, (C4) 0 to 10 wt. % ofadditives, and optionally containing one or more members selected fromthe group consisting of activators pigments, thixotrophy auxiliaries,and plasticizers.
 12. An article of manufacture comprising the filleraccording to claim 1 or 2 in cured form.
 13. An article of manufacturecomprising the filler according to claim 3 in cured form.
 14. Thearticle of manufacture according to claim 12 wherein the article ofmanufacture is selected from the group consisting of a filling, cement,temporary crown, a temporary bridge material, veneer plastic,prosthesis, orthodontic appliance, plastic seal and a plastic model. 15.The article of manufacture according to claim 13 wherein the article ofmanufacture is selected from the group consisting of a filling, cement,temporary crown, a temporary bridge material, veneer plastic,prosthesis, orthodontic appliance, plastic seal and a plastic model.